The Sixth Doctor is an incarnation of the Doctor, the protagonist of the BBCscience fiction television series Doctor Who. He is portrayed by Colin Baker. Although his televisual time on the series was comparatively brief and turbulent, Baker has continued as the Sixth Doctor in Big Finish's range of original Doctor Who audio adventures. Within the series' narrative, the Doctor is a centuries-old Time Lord alien from the planet Gallifrey who travels in time and space in his TARDIS, frequently with companions. When the Doctor is critically injured, he can regenerate his body; in doing so, his physical appearance and personality change. Baker portrays the sixth such incarnation, a flamboyant man in brightly coloured, mismatched clothes whose brash and overbearing personality set him apart from all his previous incarnations.

The Sixth Doctor appeared in three seasons. His appearance in the first of these was at the end of the final episode of The Caves of Androzani which featured the regeneration from the Fifth Doctor and thereafter in the following serial The Twin Dilemma, the end of that season. The Sixth Doctor's era was marked by the decision of the BBC controller Michael Grade to put the series on an 18-month "hiatus" between seasons 22 and 23, with only one new Doctor Who story, Slipback, made on radio during the hiatus, broadcast as 6 parts (at 10 minutes each) on BBC Radio 4 from 25 July to 8 August 1985, as part of a children's magazine show called Pirate Radio Four. Colin Baker had been signed up for four years,[1] as the previous actor Peter Davison had left after only three years.

Prior to its postponement, season 23 was well advanced with episodes already drafted and in at least one case distributed to cast and production. Alongside "The Nightmare Fair", "The Ultimate Evil", "Mission to Magnus", "Yellow Fever and How to Cure It", the remaining stories were still under development in a 25-minute episode format after the season was postponed. These were all dropped with the reconception of the season in mid 1985 in favour of a 14 episode story arc called The Trial of a Time Lord.[2] The Sixth Doctor also appeared in the special Dimensions in Time. There are also novels and audio plays featuring the Sixth Doctor, and the character has been visually referenced several times in the revived 2000s production of the show.

The sixth Doctor's regeneration was initially unstable, and he nearly strangled Peri before he came to his senses. Realising what he had nearly done, he initially considered going into a hermitlike existence on the planet Titan 3, only to be caught up in events on the planet Jocanda, after which he resumed his travels (The Twin Dilemma). He encountered many old foes including the Master, Daleks, Cybermen and Sontarans, and even shared an adventure with his own second incarnation in The Two Doctors. He also faced a renegade female Time Lord scientist, the Rani, who was conducting experiments on humans using the Luddite riots as a cover.

Later, the Doctor and Peri landed on the devastated planet Ravolox, which they discovered was actually Earth, moved across space with devastating consequences. Before they could discover the reason for this disaster, the TARDIS landed on Thoros Beta. What actually happened here is unclear, but initial accounts suggest that Peri was killed after being cruelly used as a test subject in brain transplant experiments and the Doctor was pulled out of time to a Time Lord space station where he was put on trial for the second time by his own race, the Time Lords. In reality the trial was a cover-up organised by the High Council. A race from Andromeda had stolen Time Lord secrets and hidden on Earth, so to protect themselves the Time Lords had moved Earth through space, burning the surface in a massive fireball and leaving it as Ravolox. The prosecutor at that trial, the Valeyard, turned out to be a possible future evil incarnation of the Doctor himself who was out to steal his remaining lives. He had also edited the Matrix recordings of the Doctor's travels; in reality Peri had survived events on Thoros Beta. The events of the trial tangled the Doctor's timeline slightly, as he left in the company of Mel, whom he technically had not yet met.

When the TARDIS is attacked by the Rani, the Sixth Doctor was somehow injured and regenerated into the Seventh Doctor; the exact cause of the regeneration, however, has never been revealed on-screen.

Doctor Who was put on hiatus for 18 months following The Trial of a Time Lord, and Colin Baker was asked to return for a single story which would have led to an event precipitating the Doctor's regeneration. As he declined to do so, there were limits as to what could be done on screen for the purposes of transitioning to a new Doctor when the series resumed with Time and the Rani and there were other unresolved questions, such as when and how the Doctor and Mel actually met. Attempts have been made by various authors to fill in these narrative gaps.

The Virgin Missing Adventures novel Time of Your Life states that the Doctor went into a self-imposed exile to avoid becoming the Valeyard. He was lured back into travelling by the Time Lords, and recruited Grant Markham as a companion. Although now travelling again, he attempted to avoid meeting Mel and recruited other companions such as history lecturer Evelyn Smythe and "Edwardian adventuress" Charley Pollard. He eventually encounters Mel accidentally during the events of the BBC Books novel Business Unusual and accepts his fate once she stows away in the TARDIS.

Pip and Jane Baker's novelisation of Time and the Rani provides the first relatively brief attempt to explain the Doctor's regeneration (specifically, that it was triggered by "tumultuous buffeting" as the Rani attacked the TARDIS). The Virgin New Adventures series suggests that the Seventh Doctor somehow deliberately killed the Sixth, because he could not become the masterplanner and manipulator that his next incarnation became, due to his fear of becoming the Valeyard. The BBC Books Past Doctor Adventures novel Spiral Scratch proposes that the Sixth Doctor died as a result of his chronal energy being drained in a confrontation with a powerful pan-dimensional entity before being snared by the Rani's beam. The unofficial, for-charity-published, novel Time's Champion by Craig Hinton and Chris McKeon consigns the events of Spiral Scratch to an alternate timeline, and makes the Sixth Doctor the eponymous Time's Champion, to save Mel from the clutches of the Time Lord God, Death. In these events, the Doctor, through the TARDIS' telepathic circuits, forces his own regeneration and then travels towards Lakertya, setting up the events of Time and the Rani.

In 2015, Big Finish Productions released The Sixth Doctor: The Last Adventure, an audio drama depicting the events leading up to the Sixth Doctor's death and regeneration.[3] According to this account, an alternative future Sixth Doctor, determined to stop the Valeyard from using parasitic creatures to steal the lives of every Time Lord to ever exist, sent a telepathic message to himself in the past. The message caused the past Sixth Doctor to fly his TARDIS to Lakertya, where he ended up exposed to radiation deadly to Time Lords. His death and subsequent regeneration into the Seventh Doctor killed the parasites, stopping the Valeyard from succeeding with his plan.

The Sixth Doctor was an unpredictable and somewhat petulant egoist, whose garish, multicoloured attire reflected his volatile personality. He was both portentous and eloquent, even for the Doctor – of whom he saw himself as the finest incarnation yet – and his unpredictability was made even wilder by his mood swings, manic behaviour, bombastic outbursts and glib, unflappable wit. His personality also displayed occasionally fatalistic overtones.

The Sixth Doctor was almost supremely confident in his abilities and did not suffer fools gladly; he sometimes seemed to endure Peri's presence far more than he actually appreciated it, and his superiority complex applied to almost everyone he encountered. His intellect could support his ego; for instance, the Sixth Doctor was the only one who was able to repair and operate the Chameleon Circuit within the TARDIS, allowing it to change shape to suit its surroundings rather than looking constantly like a police box (although the appropriateness of the TARDIS's appearance to its environment was more-or-less nil) in Attack of the Cybermen. However, not only did his melodramatic arrogance and caustic wit eventually subside, it actually hid the fact that this incarnation retained the Doctor's strong moral sense and empathy, as seen in Revelation of the Daleks, in which he showed great compassion for a dying mutant; and The Trial of a Time Lord, where he displayed outrage at his own people for their part in a plot and cover-up which resulted in the death of most of the Earth's population. Underneath his blustering exterior, he was more determined than ever in his universal battles against evil, possessed of a tenacity and a thirst to do what was right that was far more visible than ever before. Despite his often unstable demeanour, he was always ready to act when necessary, and very little – even his companions – could hope to stand in his way.

His condescension towards the universe around him also extended to his companions, especially Peri. While his use of violence against his foes and his abrasive relationship with Peri were both often criticised by fans, the violence was largely in self-defence, and his relationship with Peri had mellowed significantly when the programme returned from hiatus for Season 23's The Trial of a Time Lord.

The events surrounding the production of Doctor Who in the mid-1980s caused the Sixth Doctor's tenure to be cut short.[4]

During the Sixth Doctor's tenure in the Big Finish Productions audio plays, voiced by Baker, he appeared to be a somewhat calmer, wittier and altogether happier character (attributed in-story to the influence of companion Evelyn Smythe). In a 2001 poll in Doctor Who Magazine, Baker was voted the "greatest Doctor" of the audio plays. Baker has said that he was not given enough time in the 1980s to 'unpeel the layers' of his character.

Colin Baker wished to dress his Doctor in black, specifically black velvet, to reflect his character's darker personality.[5] Producer John Nathan-Turner, however, opted for a deliberately "totally tasteless" costume with clashing colours, a brief so demanding that designer Pat Godfrey's made several attempts which were considered too good before Nathan-Turner finally accepted the last one as "sufficiently garish".[6] Colin Baker later described the outfit as "an explosion in a rainbow factory".[5]

The Sixth Doctor wears a red plaid frock coat, with green patchwork, and yellow and pink lapels over a white shirt with red question marks embroidered in the collar (a feature of the programme since 1980), a waistcoat and large Victorian style necktie, and yellow trousers with black stripes was a pair of green ankle boots with red spats. There were many variants on the waistcoat and tie, the earliest being the knitted brown waistcoat and turquoise polka-dot tie. The waistcoat was later changed to red check, and in the following story a new red polka-dot tie appeared. The "future" version of the Sixth Doctor seen in aboard the Hyperion III (The Trial of a Time Lord) wore a stripey waistcoat and a yellow tie speckled with black stars. Baker added a cat badge to the ensemble.[7] During Baker's run in the stage play Doctor Who – The Ultimate Adventure, the original frock coat was replaced by a similar one with a red, blue and purple colour scheme.

More recently, a blue version of the original costume has appeared on covers of new BBC spin-off materials. First used in the webcast Real Time, due to the limited availability of colours for the purposes in the type of animation used, it has appeared subsequently on covers of audio dramas from Big Finish Productions.

Season 22 attracted some criticism for its violent content. Coincidentally, torture for entertainment was explored as a theme in the story Vengeance on Varos. After the 18-month hiatus, Season 23 featured a reduction of episodes produced, and the 14-part serial The Trial of a Time Lord was felt by some fans to reflect the fact that the series itself was "on trial" all this time.[8]

The Sixth Doctor was featured in a number of acclaimed comic strips drawn by John Ridgway. These featured visuals and storylines of a whimsical fantasy nature, similar to Alice in Wonderland. The Sixth Doctor was somewhat calmer and more restrained than on television. All of these comic strips appeared in Doctor Who magazine in the 1980s. Colin Baker himself wrote a comic book special called The Age of Chaos in which the Sixth Doctor and Frobisher visit an older version of Peri.